The present invention belongs to a fluid flow rate detection technology, and particularly relates to a flow rate sensor, particularly a thermal type flow rate sensor for detecting the flow rate of fluid flowing in a pipe line. The flow rate sensor of the present invention is suitably used to accurately measure the flow rate of fluid having relatively high viscosity and also suitably used for the measurement of flow rate of inflammable fluid for which abnormal temperature increase is required to be avoided.
Further, the present invention belongs to a fluid flow rate detection technology, and particularly relates to a flowmeter for measuring the instantaneous flow rate and the integrated flow rate of fluid flowing in a pipe line.
Still further, the present invention relates to a portable flowmeter which can be mounted on a pipe line through which kerosene is supplied to a kerosene burning device such as a stove, boiler or the like to measure the flow rate of kerosene, and also easily portably carried.
Still further, the present invention belongs to a liquid discharge amount control technology field, and particularly relates to a discharge amount control apparatus for liquid discharging equipment. The apparatus of the present invention is suitably used to control a sprayed (atomized) fuel oil discharging amount of an oil burner for burning fuel oil and produce desired heating power.
Various types of sensors have been hitherto used as a flow rate sensor (or flow velocity sensor) for measuring the flow rate (or flow velocity) of various fluid, particularly liquid, and a so-called thermal (particularly indirectly heated type) flow rate sensor is used because the cost can be easily reduced.
A sensor in which a thin-film heating element and a thin-film temperature sensing element are laminated through an insulating layer on a substrate and the substrate is secured to a pipe line is used as an indirectly heated type flow rate sensor. By passing current through the heating element, the temperature sensing element is heated to vary the electrical characteristic of the temperature sensing element such as the value of the electrical resistance of the temperature sensing element. The electrical resistance value (varied on the basis of the temperature increase of the temperature sensing element) is varied in accordance with the flow rate (flow velocity) of fluid flowing in the pipe line. This is because a part of the heating value of the heating element is transferred through the substrate into the fluid, the heating value diffusing into the fluid is varied in accordance with the flow rate (flow velocity) of the fluid, and the heating value to be supplied to the temperature sensing element is varied in accordance with the variation of the heating value diffusing into the fluid, so that the electrical resistance value of the temperature sensing element is varied. The variation of the electrical resistance value of the temperature sensing element is also varied in accordance with the temperature of the fluid. Therefore, a temperature sensing device for temperature compensation is installed in an electrical circuit for measuring the variation of the electrical resistance value of the temperature sensing element to suppress the variation of the flow-rate measurement value due to the temperature of the fluid at maximum.
An indirectly heated type flow rate sensor using thin film elements as described above is disclosed in JP-08-146026(A), for example.
The conventional indirectly heated type flow rate sensor is secured to a linear pipe line portion, and also the substrate of a flow rate detector or a casing which is thermally connected to the substrate is exposed from the wall surface of the pipe line to the fluid.
When the fluid is viscous fluid, particularly viscous fluid having relatively high viscosity, the flow-velocity distribution on the section perpendicular to the flow of the fluid in the pipe line is more remarkable (there is a great difference in flow velocity between the center portion and the outer peripheral portion on the section). In the case of the conventional sensor in which the substrate or the casing portion connected to the substrate is merely exposed to the fluid at the wall of the pipe line, the flow-velocity distribution has a great effect on the precision of the flow-rate measurement. This is because the flow velocity of the fluid flowing at the center portion on the section of the pipe line is not taken into consideration, but only the flow velocity of the fluid in the neighborhood of the wall of the pipe line is taken into consideration. As described above, the conventional flow rate sensor has such a problem that it is difficult to measure the flow rate of fluid accurately when the fluid is viscous fluid having relatively high viscosity.
Even when fluid has low viscosity at room temperature, it induces a problem connected to the above viscosity problem because the viscosity of the fluid increases as the temperature is lowered.
Further, the above problem is more remarkable when the flow rate per unit time is relatively low than when the flow rate per unit time is high.
The flow rate sensor is required to be used under an extremely broad temperature environment in accordance with a geographical condition, an indoor or outdoor condition, etc. Further, these conditions are added with a season condition, a day or night condition, etc., and the temperature environment is greatly varied. Therefore, there has been required a flow rate sensor which can detect the flow rate accurately under such a broad environmental temperature condition as described above.
Therefore, an object of the present invention is to provide a flow rate sensor which can accurately measure the flow rate of fluid flowing in a pipe line even when the fluid is viscous fluid having relatively high viscosity.
Further, an object of the present invention is to provide a flow rate sensor which can accurately measure the flow rate of fluid flowing in a pipe line even when the flow rate is relatively small.
Still further, an object of the present invention is to provide a flow rate sensor which can accurately measure the flow rate of fluid flowing in a pipe line under a broad environmental temperature condition.
In the conventional indirectly heated type flow rate sensor, a constant voltage is applied to the heating element to obtain a desired heating value. A part of the heating value is endothermically transferred to the fluid and the remaining part of the heating value is transferred to the temperature sensing element. Therefore, the surrounding temperature of the heating element is varied in accordance with the flow rate of the fluid. When the flow rate of the fluid is high, the temperature increase is small. On the other hand, when the flow rate of the fluid is low, the temperature increase is large.
The problem occurs when fluid, particularly liquid is extinguished for some cause. In this case, the endothermic action of the fluid is lost, so that the temperature of the temperature sensing element is sharply increased, resulting in deterioration of the flow rate sensor with time lapse.
In the case where the fluid is kerosene or other inflammable and volatile fluid, the fluid is vaporized if the fluid is supplied when the sharp temperature increase as described above arises or after the sharp temperature increase, and then if air is mixed with the fluid, ignition and explosion may occur.
Therefore, an object of the present invention is to prevent excessive increase of the surrounding (environmental) temperature of the heating element of the thermal flow rate sensor, thereby preventing the deterioration of the flow rate sensor with time elapse and the ignition and explosion of inflammable fluid to be detected.
Further, when fuel fluid such as kerosene or fuel gas is supplied to demanders, the flow rate (instantaneous flow rate) of fuel fluid to be supplied to each demander is measured and integrated to determine an integrated flow rate, and then the rate corresponding to the integrated flow rate is charged to the demander on the basis of the measurement result.
Various types of instruments are used as equipment for burning and consuming the fuel fluid at each demander side (for example, at general home), and the fuel consumption amount (flow rate per unit time) is generally different among these instruments. For example, a kerosene fan heater is used at a flow rate which is not so high (for example, 40 cc/hour), whereas a kerosene hot water supplier is used at a flow rate which is high (for example, 6,000 cc/hour).
As described above, the range of the flow rate at which the fuel fluid is supplied has been extremely broad at present, and also the precision required to flowmeters has also severer. That is, if the precision of the flow-rate measurement is within an error of 1%, the measurement error is equal to 60 cc/hour at maximum in the case of the kerosene hot water supplier, which means that it is insignificant to measure the flow rate of 40 cc/hour of the kerosene fan heater. Accordingly, in such a fuel fluid supply system, a severer precision at which the error is within 0.01% in the flow rate range from 10 cc/hour to 20,000 cc/hour has been required.
In order to support the required severe precision over the broad flow rate range as described above, there has been proposed a flowmeter in which the flow rate range is divided into plural flow rate areas, a flow passage for a low flow-rate area and a flow passage for a high flow-rate area are separately provided and flow rate sensors are separately disposed in the respective flow passages (see JP-08-240468(A) and JP-08-240469(A)).
However, such a flowmeter has a disadvantage that the structure of the measurement portion is complicated and large-scaled, resulting in increase of the frequency of occurrence of troubles, and further the number of flow rate sensors is increased.
Further, JP-02-238218(A) proposes an oil server which displays a kerosene integrated flow rate in a broad flow-rate area with high precision. However, this oil server has also the same disadvantage that the structure of the measurement portion is complicated and thus the frequency of occurrence of troubles is increased.
Therefore, the present invention has an object to provide a flowmeter which can measure the flow rate over a broad flow-rate range with high precision without complicating the structure of the measurement portion, with lowering the frequency of occurrence of troubles of the measurement portion and without increasing the number of flow rate sensors.
Further, a kerosene burning apparatus such as a stove, boiler or the like burns kerosene and produces heat to increase the temperature of air and heat the inside of a room, to heat and boil a large amount of water and to produce high-pressure steam serving as a driving source.
In a boiler 301 shown in FIGS. 26, 27A and 27B, kerosene is supplied from a tank 302 through a pipe line 303, and then burned by a burner 304 while sprayed. By using heat produced at this time, a large amount of water is boiled or high-pressure steam is produced, and the combustion gas is discharged from a funnel 305.
Further, a strainer 307 for removing foreign matter such as dust, motes, etc. is disposed between the tank 302 and the pump 306, and a flowmeter 308 for measuring the flow rate of kerosene is disposed between the pump 306 and the burner 304.
However, when minute foreign matters passing through the strainer 307 are gradually accumulated or foreign matters invade between the strainer 307 and the burner 304, these foreign matters cannot be removed and the foreign matters invade into the nozzle 309 of the burner 304, thereby closing a part of the discharge port 309a. 
In such a case, the amount of kerosene passing through the nozzle 309 is reduced and thus the burner 304 cannot exhibit its sufficient performance, resulting in reduction of the heat value produced in the boiler 301. Further, since kerosene is incompletely burned (combusted), the energy held by the kerosene is vainly dissipated to produce incomplete combustion gas such as carbon monoxide or the like, which causes air pollution.
In order to solve the above problem, there has been proposed an air fuel ratio control method for measuring the flow rate of kerosene flowing in a pipe line 303 with a flowmeter 308 disposed in the pipe line and supplying a suitably amount of air corresponding to the measurement value to burn kerosene.
According to this method, even when a part of the discharge port 309a of the nozzle 309 is closed, no incomplete combustion occurs and thus the vain consumption of the holding energy of kerosene and the air pollution due to the incomplete combustion can be prevented. If the foreign matters in the nozzle 309 is jetted from the discharged port 309a under jetting pressure of kerosene or the like, the burner 304 can exhibits its inherent performance and the heating value of the boiler 301 is restored to its normal value.
According to this method, the incomplete combustion can be prevented, however, the reduction of the heating value produced in the boiler 301 cannot be prevented. Further, if foreign matters in the nozzle 309 are not discharged from the discharge port 309a, they must be artificially removed.
The present invention has been implemented to solve the above problems, and has an object to provide a portable flowmeter which can be readily mounted on a pipe line for supplying kerosene to a kerosene burning apparatus, can measure the flow rate of kerosene instantaneously, is simple in construction and light in weight, and also can be easily carried by a worker.
Further, in a conventional burning apparatus such as an oil burner for producing flames by spraying and discharging fuel oil and then igniting the fuel oil, a discharge amount of fuel oil which is sprayed and discharged from an oil burner is controlled to obtain desired heating power. The control of the discharge amount is carried out by controlling the flow rate of the fuel oil in the pipe line (conduit line) and controlling the supply amount of the fuel oil to the oil burner.
For example, as shown in FIG. 28, a fuel oil supply pipe line 1105 connected to a fuel oil tank 1104 is connected to a fuel oil supply path 1103 of a return type nozzle 1102, and a strainer 1106 and a fixed displacement pump 1107 are disposed in this order from the fuel oil tank 1104 side in the fuel oil supply pipe line 1105. A fuel oil return pipe 1109 to be connected between the strainer 1106 and the fixed displacement pump 1107 is connected to a fuel oil return path 1108 of the return type nozzle 1102, and a flow-rate adjusting valve 1110 and a check valve 1111 are disposed in this order from the return type nozzle 1102 side in the fuel oil return pipe 1109.
In this apparatus, the fixed displacement pump 1107 is actuated to supply a desired amount of fuel oil in the fuel tank 1104 through the strainer 1106 to the nozzle 1102, and the desired amount of fuel oil thus supplied is sprayed and discharged from the nozzle 1102 while the flow amount thereof is controlled by the flow-rate adjusting valve 1110 of the fuel oil return pipe 1109. The surplus fuel oil is returned through the fuel oil return pipe 1109.
In order to further enhance the precision for the control of the fuel oil discharge amount in the apparatus, the following improvements have been recently made.
For example, JP-07-324728(A) discloses that in order to enable supply of a minute amount of fuel oil which has been difficult to be performed by the adjustment operation of only the flow-rate adjusting valve 1110, the fixed displacement pump 1107 is replaced by a pressure-variable pump, the supply pressure of fuel oil is set to a high value, and the sprayed discharge amount of the fuel oil in the range from a low sprayed discharge amount area to a high sprayed discharge amount area, that is, the supply amount of the fuel oil to the nozzle is controlled in combination of a throttle control operation of the flow-rate adjusting valve 1110.
Further, JP-06-42746(A) discloses that the flow-rate adjusting valve 1110 is replaced by an oil electromagnetic valve controlled by a controller, the fixed displacement pump 1107 is replaced by a fixed differential pressure pump controlled by a controller, a discharge amount variable pump controlled by a controller is disposed between the connection portion of the fuel oil return pipe 1109 and the fuel oil tank 1104, and an oil amount sensor is secured to the fuel oil supply pipe line 1105 at one of the suction side and the discharge side of the discharge amount variable pump. According to this publication, the suction/discharge amount of the disch arge amount variable pump is detected on the assumption that the amount of oil discharged from the return type nozzle 1102 is equal to the amount of oil sucked/discharged by the discharge amount variable pump under a stable state, and the output value to the discharge amount variable pump is corrected on the basis of the difference between the above detection value and a desired flow-rate amount calculated by the controller, thereby obtaining a desired oil discharge amount.
However, in both the above prior arts, the discharge amount is not controlled by detecting the discharge amount of the fuel oil which is actually discharged from the nozzle, so that it is difficult to quickly obtain a proper discharge amount when there occurs a trouble such as cavitation of the pump or a little clogging at the strainer, and the discharge amount control is still susceptible to improvements.
That is, when the control of the fuel oil discharge amount cannot be performed with high precision, the performance of the burner cannot be exhibited at maximum, so that a desired excellent burning state cannot be implemented. Therefore, an energy-resource wasting problem due to incomplete combustion and an air pollution problem due to incomplete combustion exhaust gas arise.
Particularly when the fuel oil supply amount is small, the effect of these problems is greater because the variation rate is increased.
As described above, there is not any flow-rate sensor which can accurately detect even a minute flow rate of liquid with quick response, and this is also a factor which makes it difficult to accurately control the discharge amount of liquid such as fuel oil or the like.
Therefore, an object of the present invention is to provide a liquid discharge amount control apparatus which can detect the amount of liquid actually discharged from liquid discharge equipment such as various types of nozzles as accurately as possible, and easily obtain a desired discharge amount on the basis of the detection result.
Further, another object of the present invention is to provide a liquid discharge amount control apparatus which can detect the flow rate accurately with high responsibility through the above discharge control operation even when the liquid is viscous fluid having relatively high viscosity or the discharge amount is relatively small, or under a broad environmental temperature condition, thereby performing feedback control with high reliability and achieving a desired discharge amount.
In order to attain the above object, according to the present invention, there is provided a flow rate sensor including a flow rate detector having a heating function and a temperature sensing function, and a pipe line for fluid to be detected which is formed so that heat from the flow rate detector is transferred to and absorbed by the fluid to be detected, wherein the temperature sensing which is affected by a heat absorption effect of the fluid to be detected due to the heat is executed in the flow rate detector, and the flow rate of the fluid to be detected in the pipe line is detected on the basis of the temperature sensing result, characterized in that a heat transfer member extending into the inside of the pipe line is provided to the flow rate detector, and the heat transfer member is formed so as to extend to at least the vicinity of the central portion on the section of the pipe line.
According to an embodiment of the present invention, the flow rate detector is constructed by forming on a substrate a thin-film heating element and a flow rate detecting thin-film temperature sensing element disposed so as to suffer the effect of the heating of the thin-film heating element.
According to an embodiment of the present invention, the heat transfer member is joined to the substrate.
According to an embodiment of the present invention, the thin-film heating element and the flow rate detection thin-film temperature sensing element are laminated on a first surface of the substrate through an insulating layer.
According to an embodiment of the present invention, the heat transfer member is joined to a second surface of the substrate.
According to an embodiment of the present invention, the dimension of the heat transfer member in the direction of the pipe line is set to be larger than the dimension in the direction perpendicular to the extension direction of the heat transfer member within the section of the pipe line.
According to an embodiment of the present invention, the pipe line is bent at a portion where the heat transfer member extends.
According to the present invention, there is provided a flow rate sensor including a flow rate detector having a heating function and a temperature sensing function, and a pipe line for fluid to be detected which is formed so that heat from the flow rate detector is transferred to and absorbed by the fluid to be detected, wherein the temperature sensing which is affected a heat absorption effect of the fluid to be detected due to the heat is executed in the flow rate detector, and the flow rate of the fluid to be detected in the pipe line is detected on the basis of the temperature sensing result, characterized in that the pipe line has a bent portion, and the flow rate detector is located on a wall at the fluid flow-out side of the pipe line which is located so as to traverse the travel direction of the fluid flowing from the fluid flow-in side of the bent portion of the pipe line.
According to an embodiment of the present invention, the flow rate detector is constructed by laminating a thin-film heating element and a flow rate detection thin-film temperature sensing element on a first surface of a substrate through an insulating layer, and joining a second surface of the substrate to the wall at the fluid flow-out side of the bent portion.
In the above invention, when the flow rate of the fluid to be detected in the pipe line is detected, a temperature detector for detecting the temperature of the fluid to be detected in the pipe line for compensation can be provided. The temperature detector preferably has the same temperature sensing function as the flow rate detector.
According to the present invention, in order to attain the above object, there is provided a flow rate sensor including a heating element and a flow rate detection temperature sensing element disposed so as to suffer an effect of heating of the heating element, wherein a flow passage for fluid to be detected is formed so that the heat from the heating element is transferred to and absorbed by the fluid to be detected, the temperature sensing which is affected by an effect of heat absorption of the fluid to be detected due to the heating of the heating element is executed in the flow rate detection temperature sensing element, heating control means for controlling the heating of the heating element is connected to a passage for supplying power to the heating element, the heating control means controls the power to be supplied to the heating element on the basis of the temperature sensing result so that the temperature sensing result is coincident with a target value, and the flow rate of the fluid to be detected is detected on the basis of the control state of the heating control means.
In an embodiment of the invention, a bridge circuit is formed by using the flow rate detection temperature sensing element, and an output indicating the temperature sensing result is obtained from the bridge circuit, and the heating control means is controlled on the basis of the output.
In an embodiment of the invention, the bridge circuit contains a temperature compensating temperature sensing element for compensating the temperature of the fluid to be detected.
In an embodiment of the invention, the heating control means is a variable resistor.
In an embodiment of the invention, a transistor is used as the variable resistor, and a signal based on the output indicating the temperature sensing result is used for the control input of the transistor.
In an embodiment of the invention, a voltage to be applied to the heating element is used as a thing for indicating the control state of the heating control means.
In an embodiment of the invention, the output indicating the temperature sensing result is input to the heating control means through response setting means.
In an embodiment of the invention, the responsibility setting means contains a differential amplifying circuit and an integrating circuit to which the output of the differential amplifying circuit is input.
In an embodiment of the invention, the output indicating the temperature sensing result is input to the heating control means through an integrating circuit.
In an embodiment of the invention, the differential amplifying circuit is connected to the pre-stage of the integrating circuit.
In an embodiment of the invention, each of the heating element and the flow rate detection temperature sensing element is formed of a thin film, and the heating element and the flow rate detection temperature sensing element are laminated on a substrate through an insulating layer.
According to the present invention, in order to attain the above object, there is provided a flowmeter including a heating element and a flow rate detection temperature sensing element disposed so as to be affected by an effect of heating of the heating element, wherein a flow passage for fluid to be detected is formed so that the heat from the heating element is transferred to and absorbed by fluid to be detected, the temperature sensing which is affected by an effect of heat absorption of the fluid to be detected due to the heating of the heating element is executed in the flow rate detection temperature sensing element, heating control means for controlling the heating of the heating element is connected to a passage for supplying power to the heating element, the heating control means controls the power to be supplied to the heating element so that the temperature sensing result is coincident with a target value, the heating control means performs ON-OFF control of the power to be supplied to the heating element on the basis of a pulse signal having the frequency corresponding to the temperature sensing result, and the flow rate of the fluid to be detected is detected by measuring the frequency of the pulse signal.
In an embodiment of the invention, a bridge circuit is formed by using the flow rate detection temperature sensing element, an output indicating the temperature sensing result is obtained from the bridge circuit, the output is processed by a differentially amplifying circuit and an integrating circuit to obtain a voltage signal, and the voltage signal thus obtained is subjected to voltage-frequency conversion to obtain the pulse signal.
In an embodiment of the invention, switching means is interposed in a passage for supplying power to the heating element, and the heating control means performs the ON-OFF control by opening/closing the switching means.
In an embodiment of the invention, a plurality of power supply passages to the heating element are provided, each power supply passage is supplied with a voltage which is different among the power supply passages, switching means is interposed in each power supply passage, and the heating control means selects one of the plural power supply passages to open/close the switching means thereof, thereby performing the ON-OFF control.
In an embodiment of the invention, when the frequency of the pulse signal arrives at the lower limit set value, the heating control means selects a power supply passage to which a lower voltage is applied, and when the frequency of the pulse signal arrives at the upper limit set value, the heating control means selects a power supply passage to which a higher voltage is applied.
In an embodiment of the invention, the selection of the power supply passage is performed by detecting a voltage signal which is obtained by processing the output indicating the temperature sensing result obtained from a bridge circuit formed with the flow rate detection temperature sensing element with use of a differential amplifying circuit and an integrating circuit.
In an embodiment of the invention, the switching means is a field effect transistor.
In an embodiment of the invention, the bridge circuit contains a temperature sensing element for temperature compensation to compensate the temperature of the fluid to be detected.
In an embodiment of the invention, each of the heating element and the flow rate detection temperature sensing element is formed of thin film, and the heating element and the flow rate detection temperature sensing element are laminated on a substrate through an insulating layer.
Further, in order to attain the above object, according to the invention, a portable flowmeter is constructed by a casing comprising a body portion and a lid portion, the body portion having at both the end portions thereof connection portions to be connected to external pipes and containing a flow pipe line penetrating therethrough, a flow rate sensor which is accommodated in the casing and detects the flow rate of fluid, a display portion for displaying a flow rate value, an operating portion for power-supplying and measuring the flow rate, and an electrical circuit for displaying on the display portion the flow rate detected by the flow rate sensor.
In order to detect the flow rate with high sensitivity, the flow rate sensor includes a flow rate detector having a heating element and a temperature sensing element formed on a substrate, a fin plate for transferring heat to fluid to be detected therethrough, and an output terminal for outputting the voltage value corresponding to the flow rate. The flow rate detector, a part of the fin plate and a part of the output terminal are preferably coated by molding.
In order to reduce the error of the flow rate measurement value due to the temperature of kerosene, it is preferable that a temperature sensor for detecting the temperature of the fluid is further accommodated in the casing.
In order to perform the temperature detection with high sensitivity, it is preferable that the temperature sensor includes a temperature detection portion having a temperature sensing element formed on a substrate, a fin plate for transferring heat to the fluid to be detected therethrough, and an output terminal for outputting the voltage value corresponding to the temperature and that the temperature detection portion, a part of the fin plate and a part of the output terminal are coated by molding.
The display portion is disposed on the upper surface of the lid portion of the casing to digitally display the measurement value of the flow rate.
The operating portion may be disposed on the upper surface of the lid portion of the casing, and comprise a power source button and a measurement button.
When the electrical circuit is constructed by a bridge circuit containing the temperature sensing element of the flow rate sensor and the temperature sensing element of the temperature sensor and outputting the voltage difference corresponding to the flow rate of the fluid, a V/F conversion circuit for converting the voltage difference corresponding to the flow rate of the fluid to a pulse signal having the corresponding frequency, a counter for counting the pulse signal, and a microcomputer for converting the frequency to the corresponding flow rate, the measurement value of the flow rate can be digitally displayed on the display portion.
The portable flowmeter may be mounted on a bypass pipe line secured to the external pipe. Alternatively, it may be mounted on a self seal coupling secured to the external pipe. When the flowmeter is mounted on the self seal coupling, it is not necessary to dispose an open/close valve, and thus a mounting work is simple.
Further, according to the present invention, in order to attain the above object, there is provided a liquid discharge amount control apparatus for discharging a desired discharge amount of liquid from liquid discharge equipment for discharging to the outside the liquid supplied through a pipe line connected to a liquid supply source by a pump, characterized by comprising a flow rate sensor for detecting the flow rate of the liquid flowing in the pipe line between the pump and the liquid discharge equipment, flow rate adjusting means for adjusting the flow rate of the liquid in the pipe line at the upstream side of the flow rate sensor, and a controller for controlling the flow rate adjusting means so that the flow rate value detected by the flow rate sensor is equal to the value corresponding to the desired discharge amount.
In an embodiment of the invention, the flow rate adjusting means comprises a flow rate adjusting valve secured to the pipe line between the pump and the flow rate sensor and/or the pump which is designed so that the discharge amount thereof is variable.
In an embodiment of the invention, the liquid is inflammable liquid, and the liquid discharge equipment is a non-return type nozzle.
In an embodiment of the invention, the liquid is fuel oil, and the liquid discharge equipment is a non-return hydraulic oil burner.
In an embodiment of the invention, the pipe line contains a passage for returning the liquid from a just upstream position of the flow rate sensor to an upstream position of the pump, a check valve is interposed in the passage and the check valve passes the liquid therethrough when the pressure difference between both sides with respect to the check valve is equal to a predetermined value or more.
According to the invention, in order to attain the above object, there is provided a liquid discharge amount control apparatus for discharging a desired discharge amount of liquid from liquid discharge equipment for discharging to the outside a part of the liquid supplied through a pipe line connected to a liquid supply source by a pump and returning the other part of the liquid through a return pipe to the pipe line, characterized by comprising: a first flow rate sensor for detecting the flow rate of the liquid flowing in the pipe line between the pump and the liquid discharge equipment, a second flow rate sensor for detecting the flow rate of the liquid returned through the return pipe, flow rate adjusting means for adjusting the flow rate of the liquid flowing in the pipe line at the upstream side of the first flow rate sensor, and a controller for controlling the flow rate adjusting means so that the value obtained by subtracting a second flow rate value detected by the second flow rate sensor from a first flow rate value detected by the first flow rate sensor is equal to the value corresponding to the desired discharge amount.
In an embodiment of the invention, the flow rate adjusting means comprises a flow rate adjusting valve secured in a pipe line between the pump and the first flow rate sensor and/or the pump which is designed so that the discharge amount is variable.
In an embodiment of the invention, the liquid is formed of inflammable liquid, and the liquid discharge equipment is a return type nozzle.
In an embodiment of the invention, the liquid is fuel oil, and the liquid discharge equipment is a return type hydraulic oil burner.
In the invention as described above, as the flow rate sensor or the first flow rate sensor and the second flow rate sensor may be used one which is provided with a flow rate detector having a heating function and a temperature sensing function and is secured to the pipe line so that the heat from the flow rate detector is transferred to and absorbed by the liquid, the temperature sensing affected by the heat absorption of the liquid on the basis of the heating being executed in the flow rate detector to detect the flow rate of the liquid in the pipe line on the basis of the temperature sensing result, and in which a heat transfer member extending into the pipe line is secured to the flow rate detector, the heat transfer member extending to at least the vicinity of the central portion on the section of the pipe line.
In an embodiment of the invention, the flow rate detector is constructed by forming on a substrate a thin-film heating element and a flow-rate detection thin-film temperature sensing element disposed so as to be affected by the effect of the heating of the thin-film heating element.
In an embodiment of the invention, the heat transfer member is joined to the substrate.
In an embodiment of the invention, the thin-film heating element and the flow-rate detection thin-film temperature sensing element are laminated on a first surface of the substrate through an insulating layer.
In an embodiment of the invention, the heat transfer member is joined to a second surface of the substrate.
In an embodiment of the invention, the dimension of the heat transfer member in the direction of the pipe line is larger than the dimension in a direction perpendicular to the extending direction of the heat transfer member on the section of the pipe line.
In an embodiment of the invention, there is further provided a temperature detection portion for detecting the temperature of the liquid in the pipe line for compensation when the flow rate of the liquid in the pipe line is detected.
In an embodiment of the invention, the temperature detection portion has the same temperature sensing function as the flow rate detector.
In an embodiment of the invention, the pump is a displacement type pump.